Metal treating furnace construction



A. M. BEEBEE, JR.. ETAL 3,195,503

METAL TREATING FURNACE CONSTRUCTION July 2o, 1965 2 Sheets-Sheet 2 Filed Sept. 27, 1961 United States Patent O q il.

METAL TREATING URNACE CONSTRUCTIN Alexander M. Beebee, lr., Webster, and Edward H. Kolibab and Donald K. Van Zile, Rochester, NX., assignors to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed Sept. 27, 1961, Ser. No. 141,123 1 Claim. (Cl. 118-641) This invention relates to a furnace for treatinU products with molten material and more particularly to improvements in such furnaces which facilitate the removal of excess molten material from the furnace floor.

There are presently many known types of apparatus which are employed to treat a workpiece with molten material. An example of such an apparatus is a tube mill in which a continuous supply of tubing is immersed in molten metal for the purpose of brazing or plating. In such processes it is inevitable that excess metal will drain or drip off of the tubing or out of the molten metal reservoir and will fall onto the floor ofthe chamber in which the treating process takes place. A common procedure in these tube mills is then to incline the licor of the heating chamber toward an opening thereinsuch that that excess metal will flow out of the chamber. However, efforts are generally made to reduce the wasted molten material which falls to the floor of the heating chamber t-o a minimum. Therefore, the flow of wasted metal will be small. Furthermore, as the metal flows away from the heating chamber toward a cooler area, it Will lose heat quite rapidly. Therefore, the excess metal will tend to harden on the inclined furnace iioor and eventually build up to a point where it must be cleaned out before further furnace operation is possible. This is due to the fact that the flow rate of the small stream of rapidly coolingT material is not sumcient to maintain it in a molten state until it has been conveyed away from the furnace floor. When a system of this type is used in a furnace having a brick oor or hearth the molten metal will seep down into the mortar between the bricks and eventually displace the furnace hoor to such an extent that the furnace floor must be dismantled before further furnace operation is possible. It can be seen in the cases outlined above that periodically the operation of the furf nace must be discontinued. A sufficient time must be allowed for the furnace to cool, and then it must be torn down and cleaned out and rebuilt. This resulting loss of time and production is quite expensive.

It is accordingly the object of the present invention to provide an improved furnace construction Vwhich may be employed in a tube mill, for example, for the purpose of eliminating the problems outlined above. This is accomplished through the use of a heating chamber Whose floor has formed therein a trough with a surface of monolithic construction. The trough is inclined toward a point of exit in the heating chamber and is located beneath a molten material reservoir so that it will collect the molten material which may fall from the reservoir or from the material being treated in the reservoir. Placed in the trough at the point of exit is an expendable plug which, when properly held in position, provides a fluid tight seal to the molten material accumulating in the trough. By employing this plug, the molten material is held within the heating chamber such that it remains in a molten condition until there has accumulated enough molten material to provide a steady, fast flow out ofthe heating chamber when the plug is removed.

The invention will be more readily understood upon reading of the following specification taken with the drawings of which:

FIGURE l is a cross sectional View taken substantially on line f-l of FlGURE 2 and showing the invention employed in a tube mill;

FEGURE 2 shows the point of exit from the heating chamber with the expendable plug and the clamping means to hold the plug in position;

FIGURE 3 is an exploded perspective view of the construction of the heating chamber exit; and

FGURE 4 is an isometric view of an alternative embodiment of the expendable plug.

Referring now to FIGURE l, there is shown the heating chamber section of a mill for brazing copper tubing. ln this mill, two tracks of copper tubing lll are immersed in a reservoir 12 of molten copper to form a doublewalled brazed tube. Disposed within the heating chamber le and Within the area of entry to the heating chamber are a plurality of Globar elements 1d which provide a temperature within the heating chamber which is sulficiently high to maintain the reservoir of molten copper 12. in a liquid condition. The floor 1S of the heating chamber is preferably composed of a refractory material of monolithic construction so that no seams or cracks are present into which molten metal may seep. Formed within the furnace iloor i8 is a trough 2t) whose surface is also of monolithic construction and which is inclined toward the front of the heating chamber which is shown to the left of the drawing in FIGURE l. Disposed within the trough 2@ at the exit point is a plug 2.?. also of refractory material and a clamping means 24 which holds the plug 22 in position. While the trough 2t) and plug Z2 are shown in FIGURE 2 as having a `semi-cylindrical shape, it is contemplated that a variety of other shapes can be used with equal success.

As the copper tubing l@ is immersed in the molten copper bath, it is inevitable that excess copper will drain or drip out of the reservoir fr?. or off of the tubing l@ as it leaves the reservoir l2 and will fall into the trough 2li directly below the reservoir l2. From this point, the excess copper runs down hill through the trough 29 to the plug 22 where it is dammed up by the plug. Thus excess molten copper collects in the trough Ztl until the plug 22 is removed and the copper drained to the outside and reclaimed. As previously stated, the temperature throughout the heating chamber 14 is sufficiently high such that the copper in the reservoir 12 as well as the excess copper in the trough 2.@ will remain in a molten condition and will not harden Within the trough. In this procedure it it necessary that a completely tight seal be maintained by the plug 22. This tight seal is imperative in order to prevent the cooler outside air from affecting the molten copper pool which would cause a rapid dissipation of heat through the highly conductive copper. lf this were allowed to occur, the collected pool in the trough 2d would egin to solidify within the trough and around the leak.

Upon draining the molten copper pool out of the trough Ztl by removal of the plug 22, the plug 22 itself and the trough area surrounding the plug will experience dimensional changes due to slight hardening of the copper during the drain-out process. Thus, it has been found desirable to employ a plug 22 of an expendable nature which may be replaced with each draining in order to insure a tight seal. The plug 22 may conveniently be made from a castable refractory material. Thus, the only cleaning process necessary is a minor scraping of the trough area surrounding the plug 22.

FEGURE 2 shows the exit from the heating chamber 14 and the apparatus which is employed to close the exit and maintain the plug 22 in position. A heavy welded `clamping member 24 is disposed in the exit such that the inner surface 25 of the top member of the clamping member Z4 bears against the top surface of the plug 22 to hold it in position. The left side of the clamping member 24, as viewed in FIGURES 2 and 3, is pivotally supported lhandle 34 mounted thereon.

E at point A by means of a cylindrical peg 27 which extends normally from the front surface 28 of the furnace. The peg 27 ts into a semi-circular portion 29 of the clamping member 24, such that a clockwise moment may be applied to the right side of the clamping member 24 without causing an undesirable lifting of the Yleft side thereof. The clamping member 24 has fixed to its right side, as shown in FIGURES 2 and 3, a member 3@ which acts as a support for a weighted lever rod 3l. rThere exists some clearance between the surface of the clamping member 24 and a top surface 32 of the furnace floor i8, which extends to the heating chamber exit, such that a downward pressure on the member Sti causes a clockwise moment about the pivot point A. Thus, the inner top surface 2S of the clamping member 24 bears upon the top surface of the plug 22 to firmly hold the plug in position. Additionally, the semicircular seam between the plug 22 and the trough Ztl may be lightly cemented on the front of the furnace to further insure the Huid tight seal. Since this cement is not exposed to the molten copper, it need not possess highly refractory properties. Upon removal of the plug 22, the cemented seam may easily be broken by a slight blow to the plug 22. This is to insure a fluid tight seal between plug 22 and the trough 20. It should be noted that since the molten copper pool in the trough 20 is never allowed to rise above the plug, the fluid tight seal need only be provided around the bottom periphery of the plug 22. An alternative means for providing this seal is shown in FIGURE 4 and is explained below. Completing the closure to the heating chamber exit is a vertically movable door 3? having a Formed in the door 33 are two slots 36 which allow passage of the tubing 10 out of the heating chamber I4. A rod 3S rests in two angled brackets 449 disposed on opposite sides of the exit to hold the door 33 in position. As shown in the drawings, the door 33 also bears against the top surface of the Y clamping member 24 and thus provides additional pressure on the plug 22. The previously mentioned clockwise moment imparted to the clamping member 24 is obtained by means of the lever rod 3l and a weight 42 which is suspended therefrom. The lever rod 31 is disposed such that one side bears upwardly against the undersurface of one of the angled brackets 4t) and a moment equal to the force of the weight 42 times the length of the effective lever arm acts downwardly on the member 30.

FIGURE 3 is a clearer picture of the elements of the heating chamber exit. When in operation, the expendable plug 22, shown in the shape of a half-cylinder, is placed within the trough 2t). The clamping member 24 is then placed overthe plug 22 with the pivoting elements 27 and 29 properly engaged. The door 33 is placed in position on top of the clamping member 24 and the rod 38 is put into place in the brackets 4d. The lever rod 31 is then cradled in a circular portion 44 of the member 30 and positioned such that the left side of the lever rod 3l bears on the undersurface of the right hand bracket 40 to impart of a downward force on the member 30 of the clamp- 111. ing member 24 to thereby hold the plug 22 iirmlyin position.

A further means for providing the aforementioned fluid tight seal is shown in FIGURE 4. In this embodiment, the cast refractory plug 22 has formed therein a spiral groove 45 along the cylindrical surface which mates with the surface of the trough 20. A heat resistant cord 46, which may be asbestos, is placed into the groove 45 such that half of the cross-section of the cord 46 is exposed beyond the cylindrical surface of the plug 22. When the plug 22 is clamped into the trough 2t), the cord46 deforms somewhat resiliently to act in the manner of a gasket to provide the fluid tight seal.

It is to be understood that the particular embodiments described herein are illustrative and that Various modications may be made without departing from the spirit and scope of this invention.

We claim:

Apparatus for treating workpieces with molten metal comprising a thermally insulated chamber, means to control the atmospheric conditions within the chamber, a reservoir for said molten metal employed in treating said workpieces, said reservoir disposed within the chamberl and spaced from the floor thereof, the atmospheric conditions being suitable to maintain the metal within the chamber in a molten condition, the chamber having a refractory floor, the floor having formed therein a distinct trough the surfacepof which is of monolithic construction and which is inclined toward a point of exit in the chamber, the cross-section of the trough being essen tially semicircular, the trough being located beneath the reservoir to collect excess molten metal falling from the reservoir and from the workpieces being treated, removable means to close the exit including a plug having an essentially semicircular cross-section corresponding to the cross-section of the trough and being disposed within the trough such that a portion of the plug extends externally of the chamber, the plug having formed therein a spiral groove such that the groove is adjacent the surface of the trough when the plug is placed therein, a cord of heat resistant material adapted to fit into the groove to provide a fluid-tight seal between the plug and the surface of the trough, and Weighted clamping means bearing directly against the top surface of the extended portion of the plug to maintain the plug rmly in position.

References Cited bythe Examiner UNITED STATES PATENTS RICHARD D. NEVIUS, Primary Examiner.

JOSEPH B. SPENCER, Examiner. 

